1. Field of the Invention
The present invention relates generally to apparatus for securing a lid to the open end of a metal container. More specifically, it relates to a machine for seaming lids to open cans using seaming rollers that are hydraulically actuated and cam guided, and which provide an adjustable seaming pressure.
2. Description of the Prior Art
It has become a common method of packaging both liquid and solid materials to place such in a metallic container, and to then close the container with a metallic lid that is joined to the container and sealed by a seam. Often the contents of such a sealed metallic container are vacuum packed, as in the case of foodstuffs, in particular.
Machines have been devised to make the seam between the lid and the container, a typical such machine being that shown in U.S. Pat. No. 2,907,293. The practice has been to utilize seaming rollers that are mechanically mounted to follow cams, the cams serving to mechanically move the seaming rollers along a fixed path and with a fixed application pressure into progressively tighter engagement with the lid and its container, until the desired seam has been formed.
These seaming machines of the past are obviously functional, and are in widespread use. However, several problems are often encountered in their use. For example, it is normally not possible to adjust the seaming roller pressure or speed in such devices, where the movement of the seaming rollers is dependent on a mechanical linkage. This can prove a problem when different thicknesses or kinds of metal are used for the container and lid, for the pressure needed or the allowable speed of seam formation in one instance to form a seam may be too great in another instance, and can cause collapse or destruction of the container.
Another problem with many current seaming machines is that complicated mechanical linkages are involved, which over time tend to wear to the point where malfunctions occur, and extensive repairs and replacement of parts must be undertaken. Such repairs can involve considerable downtime and expense, which is compounded by the losses due to the machine being out of service for an extended period.
There is a need for a seaming machine that is simply designed so that parts can be easily replaced, which is fully and easily adjustable in operation to accomodate different containers and lids, and which will generally avoid the operational problems encountered with conventional seaming machines utilizing cam driven seaming rollers. The present invention is intended to satisfy that need.